Hydroxylamine has found many uses in a variety of industries. In the pharmaceutical industry for the preparation of specialty drugs and in connection with stripping compositions for photoresists within the microelectronic industry it has found wide use. In both the pharmaceutical industry and for photoresist and residue removal treatment it is important that the product is free of metal cation and anion impurities.
The use of ion exchange for purifying hydroxylamines is well known. However, resin conditioning and regeneration in the purification process of the prior art has not dealt with the reduction of trace metals or the possibility of exothermic reactions resulting from the decomposition of hydroxylamine.
Additionally, the order of ion exchange is critical to maintaining stability of the hydroxylamine within the ion exchange cylinder. It has been found that anion exchange followed by cation exchange can lead to rapid decomposition of hydroxylamine and produce explosive consequences within the cation resin cylinder.
U.S. Pat. No. 4,147,623 of Koff et al., which is herein incorporated by reference, discloses the purification of hydroxylamine by ion exclusion which includes use of anion exchange resin in which hydroxylammonium salts are passed. The ion exchange resin is primarily utilized as a reaction source for the hydroxylamine salt neutralizer on a small scale rather than for separation of metal cation and anion impurities.
U.S. Pat. No. 4,202,765 to Koff et al., which is herein incorporated by reference, discloses the separation of hydroxylamine from a solution of hydroxylammonium salt through the use of a cation exchange resin. The process does not teach the removal of anions or the use of anion exchange resins.
U.S. Pat. No. 5,318,762 to Cawlfield et al. discloses treating solutions of hydroxylammonium salts containing excess acid by passing the solutions through a weak base ion exchange resin.
U.S. Pat. No. 4,166,842 discloses a process of extracting hydroxylammonium ions from a solution utilizing a cation exchange resin which included the further step of converting the hydroxylammonium ions to hydroxylamine.
None of the prior art teach the removal of cations and anions from hydroxylamine so as to produce a highly purified hydroxylamine having a low concentration of sodium, potassium, and other metal ions.